Songbirds depend on acoustic communication to attract mates and defend territories. The communication channel of vocalizing animals is called signal space, a multidimensional area defined by temporal and spectral signal features. The availability of signal space depends upon ambient noise, the number of competitors for the space, and the extent of song overlap among species within an acoustic community. To minimize acoustic interference, sympatric species should inhabit a well-defined acoustic niche. Partitioning of signal space results from signal evolution in favor of species-specific song, but also occurs through behavioral adjustments to avoid overlap. Additionally, songs of closely-related species may be less similar than songs of phylogenetically distant species, suggesting divergence of songs to prevent hybrid matings. We hypothesize that warbler species partition signal space, and test whether phylogenetic distance between species predicts overlap within that space. We recorded songs of 10-15 focal males per species from a community of warblers that co-occur at Fort Drum, New York.
Results/Conclusions
To generate signal space axes, we ran a principal components analysis of song characteristics, yielding three significant PCs which collectively explained 88% of variation among species and reflected heavy loading of frequency traits (PC1), temporal traits (PC2), and bandwidth (PC3). Most species inhabited clearly partitioned acoustic space, with interspecific variation in area occupied and little overlap among species. Preliminary analysis of distances between acoustic niches suggests that songs of phylogenetically closer species are more similar than those of more distant species. Our study is a critical step in understanding partitioning of signal space in communities, and how signal overlap can drive signal evolution. Additionally, our findings inform further research into ways environmental disturbances may drive community-wide shifts of acoustic niches.